make it possible to use "start" and "atok" as literal tokens

parser-tools-lib/parser-tools/cfg-parser.rkt

@@ -489,6 +489,12 @@
                                                 (fail-k max-depth tasks))))])
                  (k end max-depth tasks new-got-k new-fail-k)))])))))
 
+;; These temp identifiers can't be `gensym` or `generate-temporary`
+;; because they have to be consistent between module loads
+;; (IIUC, the parser is multi-threaded, and this approach is not thread-safe)
+;; so I see no alternative to the old standby of making them ludicrously unlikely
+(define-for-syntax start-id-temp 'start_jihqolbbafscgxvsufnepvmxqipnxgmlpxukmdoqxqzmzgaogaftbkbyqjttwwfimifowdxfyekjiixdmtprfkcvfciraehoeuaz)
+(define-for-syntax atok-id-temp 'atok_wrutdjgecmybyfipiwsgjlvsveryodlgassuzcargiuznzgdghrykfqfbwcjgzdhdoeqxcucmtjkuyucskzethozhqkasphdwbht)
 (define-syntax (cfg-parser stx)
   (syntax-case stx ()
     [(_ clause ...)
@@ -704,11 +710,17 @@
                                                        [(pos ...) 
                                                         (if src-pos?
                                                             #'($1-start-pos $1-end-pos)
-                                                            #'(#f #f))])
+                                                            #'(#f #f))]
-                                           #`(grammar (start [() null]
+                                                       ;; rename `start` and `atok` to temp ids
-                                                             [(atok start) (cons $1 $2)])
+                                                       ;; so that "start" and "atok" can be used as literal string tokens in a grammar.
-                                                      (atok [(tok) (make-tok 'tok-id 'tok $e pos ...)] ...)))
+                                                       ;; not sure why this works, but it passes all tests.
-                                         #`(start start)
+                                                       [%start start-id-temp]
+                                                       [%atok atok-id-temp])
+                                           #`(grammar (%start [() null]
+                                                              [(%atok %start) (cons $1 $2)])
+                                                      (%atok [(tok) (make-tok 'tok-id 'tok $e pos ...)] ...)))
+                                         (with-syntax ([%start start-id-temp])
+                                           #`(start %start))
                                          parser-clauses)))]
                                [(grammar . _)
                                 (raise-syntax-error